1. Field of the Invention
This invention relates to aircraft exit door locking systems and, more particularly, to automatic locking systems which prevent inadvertent operation of aircraft exit opening means during flight.
2. Description of the Prior Art
Currently, Part 25 of the Federal Aviation Administration (F.A.A.) Regulations requires that aircraft exits be protected against inadvertent opening in flight by persons. The F.A.A. Regulations also require that operation of a single handle be used to open an aircraft exit. The requirement for a single handle prevents the use of manually operated locks to prevent handle operation.
To meet these requirements, aircraft exits have previously been designed such that pressurization loads in flight prevent operation of the handle. However, the point where pressurization loads exceed the mechanical advantage at the handle, occurs after the aircraft has become airborne and pressurized to the appropriate level. The altitude at which the exit becomes locked is variable due to pressurization schedule, atmospheric conditions and exit linkage design.
Further prior designs have incorporated a flight lock system which was activated by air/ground logic controlled by the landing gear truck tilt. As the aircraft main body and wing landing gear departed the ground the rotation of the gear trucks would activate switches which in turn would energize an electromechanical actuator thereby rotating a pawl into a position of interference with the exit handle thus preventing rotation while in flight.
U.S. Pat. No. 3,829,834 is representative of the patent literature prior art and shows a predetermined combination of manually operated switches to actuate a motor for unlocking purposes.
It is accordingly an object of the present invention to provide an automatically engaged and disengaged exit door flight lock system.